Having failed to stop Obamacare in the Supreme Court or the presidential election, conservatives still might sabotage at least part of it in such GOP-controlled states as Virginia.

Gov. Bob McDonnell and some fellow Republicans in the legislature are considering blocking one of the program’s key reforms: extending Medicaid, the federal health insurance program for the working poor.

That would be a costly mistake, for two reasons. First, it would mean a missed opportunity to help hundreds of thousands of Virginians struggling to make ends meet.

The potential recipients aren’t deadbeats, as opponents of the health law often make them out to be. More than two-thirds are in households where someone works but does not earn enough to afford private health insurance.

One is Jesse Carr, 58, of Leesburg. The former Navy Seabee earns $11 an hour as a home health-care worker. He gave up health insurance six years ago because it was too expensive. That means he can’t get a colonoscopy or dental work he knows he needs.

“If you’ve got a job with insurance, you’re lucky,” Carr said. “A lot of people don’t have it. Anybody who waits on you at a restaurant probably doesn’t have it.”

Virginia Republicans said initially that helping people like Carr is a luxury the state can’t afford.

But it turns out that judgment was based on faulty arithmetic. That’s the second reason Medicaid should be extended.

Because of how Obamacare is structured, states give up billions of dollars in federal grants if they keep Medicaid unchanged. Republican governors have sheepishly conceded that point with dramatic turnarounds to accept the expansion in Ohio, Arizona and elsewhere.

The same logic holds for Virginia. In the first five years of the Affordable Care Act, according to an analysis by the Virginia Hospital and Healthcare Association, the Old Dominion would forgo receiving $9.9 billion for Medicaid payments to Virginia citizens if it refused to expand the program.

Moreover, regardless of what the state does, Virginians will pay $10.2 billion in extra taxes because of Obamacare.

Which would you rather do? Pay more than $10 billion in taxes and get none of it back for benefits? Or get back nearly all of it if you’re willing to swallow your pride and set aside your reflexive anti-government ideology?

In addition, looking just at the state budget over the five years, expanding Medicaid would yield a net benefit for Virginia of $317 million.

In light of those numbers, McDonnell and some other Virginia Republicans have started hedging their bets as the moment of decision approaches in the current General Assembly session.

Many in the GOP are now saying they might extend Medicaid after all, provided the move is accompanied by reforms to curb the cost of the program. (They also want an option to pull back if the federal government scales back its promised payments.)

I’m all for such reforms, in principle. They would help fulfill one of Obamacare’s overlooked goals of reining in health-care costs. Worthy changes would include reducing unneeded emergency room visits and medical tests.

In practice, though, there’s a fair chance that Virginia Republicans will use the need for cost-cutting as an excuse to prevent Medicaid from expanding at all.

If they did so, it would be largely because they can’t get past the mistaken idea that the people who’d benefit don’t deserve the help.

“There seems to be a misimpression about who these folks are. They are hardworking people who’ve done everything right . . . but the price [of health insurance] kept going up and up, or all of a sudden their employer dropped it,” said Deborah Oswalt, executive director of the Virginia Health Care Foundation.

Consider Vellon Harris, 48, of Arlington. Like Carr, she’s a home health worker who cares for mostly elderly patients. Her wages, $11.46 an hour, are covered by Medicaid. But she earns too much to be eligible for that program and can’t afford private insurance herself.

Harris can’t afford doctor’s visits and relies on the emergency room when necessary, such as when she needed surgery to remove gallstones a year ago. When she got sick with flulike symptoms in late November, she suffered through it.

“No money, no anything. I was tired, sweating, aching. I couldn’t get up, couldn’t eat,” Harris said. “I lay there. I couldn’t do anything but pray.”

For the sake of budget sense and common decency, Virginia shouldn’t turn down billions of dollars to improve life for Harris and others like her.

For previous Robert McCartney columns, go to washingtonpost.com/mccartney.